Piezo-electric igniter



OC- 31 1957 w. MALTNER rami. 3,350,608

PIEZO-ELECTRIC IGNITER Filed sept. 2l, 1954 United States Patent O 3,350,608 PIEZU-ELECTRHC IGNITER Wolfgang Maltner, Oberstedten, Taunus, and Horst Dieterle, Frankfurt am Main, Germany, assigner-s to Heinrich Meitner G.m.b.H., Offenbach am Main, Germany Filed Sept. 21, 1964, Ser. No. 397,801 Claims priority, application Germany, Sept. 21, 1963, M 58,290 12 Claims. (Cl. 317-96) The present invention relates to igniters in general, and more particularly to a piezo-electric igniter for lighters or the like. Still more particularly, the invention relates to a piezo-electric igniter of the type wherein tension or compression in the direction of a piezo-electric axis in a single or composite transducer crystal generates an electrostatic voltage which is utilized to produce one or more sparks and to thus ignite a jet of gaseous fuel or a fuel-impregnated wick in a table lighter or the like.

It is well known that compression of a piezo-electric crystal in the direction of its piezo-electric axis generates a high voltage which may be used to produce a spark between a pair of suitably spaced electrodes. The process is reversible because the crystal will generate voltage in response to tension, i.e., in response a reduction of compressive stress. For example, when a crystal is used in a piezo-electric igniter for lighters, compression of the crystal 4*generates one or more sparks which are used to ignite the fuel, but a subsequent reduction of compressive stress again produces one or more sparks which are undesirable and which might cause a shock to the operator. It was assumed that, once the expanding crystal has produced one or more additional sparks, the voltage returns to zero unless the stress generating mechanism is operated on purpose in order to produce a fresh set of sparks when the operator again decides to utilize the lighter. However, in actual practice, the voltage does not return to zero when the crystal is free to expand, even if the voltage generated during expansion ha-s produced one or more sparks, so that the igniter is likely to cause a shock to the operator even when the lighter is not in use but is merely touched by a person. Actual experiments indicate that the above problems also arise in igniters wherein the stress generating mechanism is completely disengaged from the crystal so that the crystal is normally not subjected to any compressive stresses. It was also found that the situation 4remains the same if the crystal is a composite structure which is assembled of crystals consisting of the same material or materials. In other words, one can say that the presence of some potential between the poles of a piezo-electric transducer crystal which is not subjected to any stresses is simply a phenomenon which must be accepted as a characteristic feature of such crystals. For example, in a miniature lighter wherein the igniter must produce a voltage in the range of several kilovolts, even the best insulation cannot prevent leaking currents according to which there is no exact reversibility and the potential of the piezo-electric transducer does not return to zero.

Accordingly, it is an important object of the present invention to provide an improved piezo-electric igniter for lighters and the like which is constructed and assembled in such a way that the presence of residual electric charge between the poles of an unstressed transducer crystal does not in any way affect the utility and/or safety of such devices.

Another object of the invention is to provide a piezoelectric igniter wherein the presence of residual potential difference between the poles of an unstressed transducer crystal cannot cause a shock to -a person who happens of different to touch the apparatus in which the igniter is installed.

A further object of the invention is to provide a piezoelectric igniter of the above outlined characteristics which is an exceptionally compact, rugged, reliable and easy-to-handle device capable of being installed in cornparatively large lighters as well as in miniature lighters or similar devices wherein electrical energy is to be generated without resorting to batteries, household outlets and similar sources of electrical energy.

Still another object of the invention is to provide an igniter wherein the fact that the igniter is shockproof does not affect its utility in a, lighter or the like, and wherein a voltage in the range of several kilovolts may be produced by finger pressure to initiate ignition of a ame at the discretion of the operator.

A concomitant object of the instant invention is to provide an igniter whose piezo-electric transducer crystal is automatically prevented from causing ignition of a flame as soon as the operator decides to release the stress generating mechanism of a lighter in which the igniter is put to use, and wherein the customary electrodes which are used to deline the spark gap may also serve as a safety device to render the igniter shockproof.

An additional object of the invention is to provide an igniter whose stress generating mechanism automatically returns to its initial or starting position as soon as its actuating member is released by the operator so that the igniter is ready for immediate reuse.

Briefly stated, one feature of our invention resides in the provision of a piezo-electric igniter, particularly for use in table lighters or the like. This igniter comprises a simple or composite piezo-electric transducer crystal having a pair of poles located at the opposite ends of its piezoelectric axis, a stress generating mechanism for subjecting the crystal to compressive stresses acting between the poles so that the crystal generates an electrostatic voltage which may produce one or more sparks to initiate ignition of a jet of gaseous fuel or a fuel-impregnated wick, an actuating member which forms part of the stress generating mechanism and which may be manipulated manually t0 move an initial or starting position to a second position and to thereby effect compression of the crystal, and a pair of electrodes normally in current-conducting contact with each other and each connected with one pole of the crystal to short-circuit the crystal. In accordance with our invention, one of the electrodes is movable away from the other electrode in response to movement of the actuating member from its starting position so that the circuit of the crystal is open at the time the latter produces an electrostatic voltage which is used to produce one or more sparks. Such spark or sparks may be produced between the aforementioned electrodes which, at the time the crystal undergoes suicient compression to generate la required voltage, are spaced apart sufficiently do define la spark gap. Alternatively, the spark may be produced between a second pair of electrodes which are permanently spaced apart and each of which is connected with one of the aforementioned electrodes. In such modied igniters, the distance between the first mentioned electrodes must exceed the distance between the second pair of electrodes not later than at the time the crystal has undergone requisite compression.

The novel features which .are considered as characteristic of the invention are set forth in the appended claims. The improved igniter itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with .reference to the accompanying drawings, in which:

The single figure is a longitudinal vertical section through a piezo-electric igniter which is constructed in Aaccordance with my invention and comprises two pairs of electrodes.

Referring to the drawing, there is shown a piezo-electric igniter resembling the one which is disclosed in the copending application Ser. No. 397,800 of Wolfgang Maltner. This igniter comprises an elongated, substantially U- shaped holder 1 for a tubular insulator 2 which supports a pair of piezoid transducer crystals 3, 4. The crystals are movable in the longitudinal direction of the insulator 2, i.e., in the direction of their piezo-electric axis, and their inner poles abut against a plate-like conductor 5. The conductor 5 is connected with a con-ductor wire 6 extending through the insulator 2 and on to a first electrode 7. A second electrode 8 is provided at the tip of a bracket 9 which is connected to the holder 1. The holder is conductively connected to the outer poles of both crystals in a manner to be presently described. The igniter also comprises a stress generating mechanism including an actuating lever 17 which is rockable about a pivot pin 18 fixed to the holder 1 to the left of the crystal 4. This pivot pin extends through a downwardly Iextending lug 17a of the actuating lever 17 and supports a second pivot pin 19` for 4a. stress transmitting link 15 bearing against .a stress transmitting plate 16 which abuts against the left-hand pole of the crystal 4, i.e., the left-hand pole of this crystal is eonductively connected with the holder through the link 15, pin 19, lug 17a and pin 18. The right-hand pole of the crystal 3 abuts against a stress transmitting plate 14 which in turn abuts against the leftmost dished spring of a package 13 containing two pairs of such springs. The package 13 is disposed between the plate 14 and a further plate 12 which bears against the tip of an adjustable stop screw 10 meshing with an internally threaded blockshaped carrier 11 which is fixed to the holder 1. Thus, the right-hand pole of the crystal 3 is conductively connected with the holder through the plates 12, 14, package 13, screw 10 and carrier 11. The lever 17 and link 15 constitute a single-stage toggle mechanism which is utilized to subject the crystals to compressive stresses in response to clockwise rotation of the lever 17, see the arrow P. The lever 17 is permanently biased to the initial or starting position by a helical spring 20 which operates between the supper side of the insulator 2 and a median portion of the lever.

In accordance with the present invention, the insulator 2 comprises a rearwardly and upwardly extending extension or arm 2a which is adjacent to the trailing or free end of the lever 17. The `wire 6 is connected with a similar conductor 22 extending into the arm 2a and having a bare electrode or terminal 23 which normally abuts against fa U-shaped electrode or terminal 21 secured to the rear end of the lever 17. The terminal 21 is conductively connected with the `holder 1 through the lever 17 and pin 18. When the spring 20 is free to expand, the terminals 21, 23 are in actual Contact and complete the circuit of the crystals 3, 4. It will be noted that the crystals 3, 4 constitute a composite crystal one pole of which (namely, the end faces vabutting the plates 14, 16) is connected with the holder 1 and the other poles of which (namely, the end faces abutting the plate 5) is connected with the conductors 6, 22 so that this composite -crystal is normally short-circuited because the terminals 21, 23 contact each other when the spring 20 is free to expand.

The igniter shown in the drawing is operated as follows:

When the operator desires to operate a lighter in which the igniter is installed, he exerts a force in the direction indicated by the arrow P so that the terminal 21 moves away from the terminal 23 and the circuit of the crystals 3, 4 is open. The link 15 bears against the plate 16 and shifts the crystals 3, 4 axially in order to compress the package 13. Once the package ceases to yield, it acts as an extension of the stop screw 10 and plate 12 whereby the link begins to compress the crystals in the direction of their piezo-electric axis if the operator continues to pivot the lever 17 in clockwise direction. Such compression causes the crystals to generate an electrostatic voltage which produces one or more sparks across the gap between the electrodes 7, S. Such spark is invariably produced between the electrodes 7, 8, not between the terminals 21, 23 because, at the time the crystals have generated a voltage high enough to produce a spark across the gap between the electrodes, the distan-ce between the terminals 21, 23 exceeds the distance between the electrodes.

When the operator thereupon releases the lever 17 so that the spring 20 may expand, the crystals again generate a Voltage high enough to produce a spark across the gap between the terminals 21, 23 which move toward each other. This means that, once the lever 17 returns to the initial position, the opposite poles of the crystals 3, 4 are conductively connected to each -other and the user is protected from accidental shocks.

The screw 10 will be adjusted for the purpose of compensating for the wear on the stress generating mechanism and also to compensate for eventual inaccuracies in the machining of individual parts. Invariably, the length of angular movement to be performed by the lever 17 in order to compress the package 13 exceeds the length of angular movement which is necessary to subject the crystals 3, 4 to requisite compression. The angular movement necessary to compress the crystals may be inthe range of a few hundredths of a millimeter. The terminals 21, 23 serve the additional purpose of arresting the lever 17 in its initial position against the bias of the spring 20. This spring is prestressed, and it is also preferred to insert the package 13 in at least slightly prestressed condition. When the lever 17 is pivoted to its second position in which the crystals produce a spark across the gap between the electrodes 7, 8 the terminal 21 has moved through a distance of several millimeters and the width of the gap between the terminals 21, 23 then exceeds at least slightly the' maximum width of the gap between the electrodes. The fact that the `maximum distance between the terminals 21, 23 exceeds the width of the gap between the electrodes is also attributable to the provision of the package 13 which necessitates some lost motion of the lever 17 before the link 15 begins to actually compress the crystals 3 and 4. In other words, the likelihood that the voltage generated by the crystals 3, 4 in response to pivoting the lever 17 in a clockwise direction would produce a spark across the gap between the terminals 21, 23 is non-existent because, at the time the link 15 begins to compress the crystals, the distance between the terminals 21, 23 already exceeds the width of the gap between the electrodes.

The terminals 21, 23 automatically connect the poles of the crystals 3, 4 as soon as the lever 17 returns to its initial position. At the same time, the terminals 21, 23 arrest the lever in such initial position and thus ke'ep the lever in a state `ready for the next operation. It is clear that the terminal 21 may be mounted on the lever 17 or on another movable part of the stress generating mechanism in such a way that it lcornes in contact with the terminal 23 even before the lever 17 returns all the way to its initial position. However, the construction shown in the drawing Iis normally preferred because the terminals 21, 23 then serve to terminate the mechanical and electrical effectiveness of the igniter as soon as the lever reaches the position shown in the drawing.

The improved igniter may be modified in a number of ways without departing from the scope of our invention. For example, the insulator 2 may consist of several sections which are movable with the crystals 3, 4. Also, the stress generating mechanism may be replaced by another type of mechanism, for example, by a multi-stage toggle mechanism wherein the lever 17 is connected with the link 15 through the intermediary of one or more additional levers, links or similar elements. The terminal 21 need not be directly -connected with the lever 17 as long pa as it moves away from the terminal 23 when the lever is moved from its starting position. Also, the configuration of the holder 1 may be modilied in a number of ways so that the igniter may be installed in any desired type of lighter.

It is also possible to provide the igniter with a discharge resistance whose resistance value is such that it prevents discharge of a spark at the time the crystal or crystals undergo compression or tension. The resistance will enable the crystal to generate a spark subsequent to srelease the actuating member, i.e., when the actuating member returns to its initial position. For example, the spark may be produced one or more seconds after the lever 17 or 23 is released. The crystal then constitutes the capacitor of an R-C unit whose time constant may be readily selected in such a way that it exceeds the length of time necessary to complete a stress generating and relieving stroke. In other words, the R-C would permit a spark to jump across the gap between the electrodes 7 and 8 immediately or shortly `after the lever 17 has been pivoted from its initial position and has thereupon returned to such initial position.

Without further analysis, the yforegoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations should and are intended to be -comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a piezo-electric igniter, particularly for use in lgihters and the like, in combination, a transducer crystal having a pair of poles; stress generating means arranged to subject said crystal to compressive stresses in the direction of its piezo-electric axis so that the crystal generates a voltage, said stress generating means comprising actuating means movable from a starting position to a second position to thereby eifect compression of said crystal; and a pair of conductors normally in current-conducting contact with each other and each connected with one of said poles to short-circuit said crystal, one of said conductors being movable away from the other conductor in response to movement of said actuating means from said starting position to thereby terminate the current-con` ducting connection between said poles.

2. In a manually oper-able piezo-electric igniter, particularly for use in lighters and the like, in combination, a transducer crystal having a pair of poles; a stress generating mechanism for subjecting the Icrystal to compressive stresses acting in the direction of its piezo-electric axis so that the crystal generates a voltage, said mechanism comprising a manually operable actuating member movable from a starting position to a second position to thereby effect compression of said crystal; and a pair of conductors normally in current-conducting contact with each other and each connected with one of said poles to short-circuit said crystal, one of said conductors being connected with said actuating member to move away from the other conductor in response to movement of said actuating member from said starting position to thereby terminate the current-conducting connection between the said poles.

3. In a manually operable piezo-electric igniter, particularly for use in lighters and the like, in combination, a transducer crystal having a pair of poles; a stress generating mechanism for subjecting the crystal to compressive stresses acting in the direction of its piezo-electric axis so that the crystal generates a voltage, said mechanism comprising a manually operable Vactuating member movable from a starting position to a second position to thereby effect compression of said crystal; and a pair of conductors normally in current-conducting contact with each other .and each connecting with one of said poles to short-circuit said crystal, one of said conductors being fixed and the other conductor being connected with said actuating member to move away from said one conductor in response to movement of said actuating member from said starting position to thereby terminate the currentconducting connection between the poles, said conductors being arranged to automatically arrest the actuating member in said starting position when said other conductor engages said fixed conductor.

4. In a manu-ally operable piezo-electric igniter, particularly for use in lighters and the like, in combination, a. transducer crystal having a pair of poles disposed at the opposite ends of its piezo-electric axis; a str'ess generating mechanism for subjecting the crystal to compressive stresses acting in the direction of said -axis so that the crystal generates a voltage, said mechanism comprising a lixed pivot and a manually operable actuating lever pivotable about said pivot from a starting position to a second position to thereby eifect compression of said crystal, said manually operable lever having a portion distant from said pivot; and a pair of conductors normally in current-conducting contact with each other and each electrically connected with one of said poles lto shortcircuit said crystal, one of said conductors being fixed and the other conductor being connected to said portion of said manually operable lever to move away from said one conductor in response to pivotal movement of the manually operable lever from said starting position to thereby 'terminate the current-conducting connection between said poles.

5. In a piezo-electric igniter, particularly for use in lighters and the like, in combination, a transducer crystal having a pair of poles; stress generating means arranged to subject said crystal to compressive stresses in the direction of its piezo-electric axis so that the crystal generates a voltage, said stress generating means comprising actuating means movable from a starting position to a second position to thereby effect compression of said crystal; and two conductor means, -comprising a first pair of conductor portions normally in current-conducting contact with each other and each connected with one of said poles to shortcircuit said crystal, one of said conductor portions being movable away from the other in response to movement of said actuating means from said starting position to thereby terminate the current-conducting connection between said poles, and a second pair of conductor portions delining between themselves a spark gap, each conductor portion of said second pair being electrically connected with one conductor portion of said first pair.

6. A structure as set forth in claim 5, wherein the distance between the conductor portions of said iirst pair exceeds the width of said spark gap when the actuating means is moved to said second position so that the spark produced by voltage generated on compression of said crystal develops across the gap between the conductor portions of said second pair.

7. In a piezo-electric igniter, particularly for use in lighters and the like, in combination, a transducer crystal having a pair of poles disposed at the opposite ends of its piezo-electric axis; movable stress generating means arranged to subject said crystal to compressive stresses acting in the direction of said axis so that the crystal generates an electrostatic voltage, said stress generating means comprising actuating means movable with lost motion from a starting position to a second position to thereby eiect compression of said crystal; and a pair of conductors normally in current-conducting contact with each other and each electrically connected with one of said poles to short-circuit said crystal, one of said conductors being movable away from the other conductor in response to movement of said actuating means from said starting position to thereby terminate the current-conducting connection between said poles.

8. A structure as set forth in claim 7, further comprising resilient means interposed in the path of movement of said stress generating means to effect said lost motion of the actuating means prior to actual compression of said crystal.

9. A structure as set forth in claim 7, further comprising fixed stop means and resilient means interposed between said stop means and one pole of said crystal, said stress generating means comprising `a stress transmitting member arranged to transmit compressive stresses to the other pole of said crystal in response to movement of said actuating means from said starting position and subsequent to deformation of said resilient means so that the resilient means causes said lost motion.

10. In a piezo-electric igniter, particularly for use in lighters and the like, in combination, a transducer crystal having a pair of poles; stress generating means arranged to subject said crystal to compressive stresses in the direction of its piezo-electric axis so that the crystal generates a voltage, said stress generating means comprising actuating means movable from a starting position to a second position to thereby effect compression of said crystal; and short circuiting means for establishing an electrical conne'ction between said poles in response to movement of said actuating means to said starting position and for terminating end electrical connection in response Vto movement of said actuating means to said second position, said short circuiting means defining upon such termination a spark gap across which said Voltage can discharge.

11. A structure as set `forth in claim 10, wherein said short circuiting means comprises a pair of electrodes dening said spark gap and each connected with one of said poles, said short-circuiting means further comprising .a discharge resistor whose resistance is such that the voltage generated during compression and subsequent eX- pansion of said crystal produces a spark across said gap following the return ofv said crystal to uncompressed condition.

12. A piezo-electric igniter, comprising holder means; a piezo-electric transducer crystal mounted on said holder means .and arranged to generate a high voltage in response to compression in the direction of its piezo-electric axis, said crystal having a pair of poles disposed at the opposite ends of said axis; a mechanism for compressing said crystal; first electric conductor means connected with one of said poles and including a first electrode; second electric conductor means connected with the other of said poles and including a second electrode spaced from said first electrode to form therewith a spark gap at least when said crystal undergoes compression 4by said mechanism so that the voltage generated by said crystal produces a spark across said gap, said first and second conductor means being insulated from each other; and short-circuiting means lfor electrically connecting said poles to each other when said crystal is not compressed by said mechanism.

References Cited UNITED STATES PATENTS 2,248,574 7/1941 Knight 123-148 2,717,916 9/ 1955 Harkness 123-148 2,954,506 9/1960 Harkness 310-8.3 3,118,074 1/ 1964 losephson et al 31o-8.7 3,147,401 9/1964- Worting 317-97 3,167,687 1/1965 Buitkus 317-83 3,211,949 10/1965 Slaymaker et al 315-55 FOREIGN PATENTS 712,803 7/1954 Great Britain.

RICHARD M. WOOD, Primary Examiner.

V. Y. MAYEWSKY, Assistant Examiner. 

1. IN A PIEZO-ELECTRIC IGNITER, PARTICULARLY FOR USE IN LIGHTERS AND THE LIKE, IN COMBINATION, A TRANSDUCER CRYSTAL HAVING A PAIR OF POLES; STRESS GENERATING MEANS ARRANGED TO SUBJECT AS CRYSTAL TO COMPRESSIVE STRESSES IN THE DIRECTION OF ITS PIEZO-ELECTRIC AXIS SO THAT THE CRYSTAL GENERATES A VOLTAGE, SAID STRESS GENERATING MEANS COMPRISING ACTUATING MEANS MOVABLE FROM A STARTIANG POSITION TO A SECOND POSITION TO THEREBY EFFECT COMPRESSION OF SAID CRYSTAL; AND A PAIR OF CONDUCTORS NORMALLY IN CURRENT-CONDUCTING CONTACT WITH EACH OTHER AND EAC CONNECETED WITH ONE OF SAID POLES TO SHORT-CIRCUIT SAID CRYSTAL, ONE OF SAID CONDUCTORS BEING MOVABLE AWAY FROM THE OTHER CONDUCTOR IN RESPONSE TO MOVEMENT OF SAID ACTUATING MEANS FORM SAID STARTING POSITION TO THEREBY TERMINATE THE CURRENT-CONDUCTING CONNECTION BETWEEN SAID POLES. 